JPH10266274A - Hydraulic circuit device of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent operability and workability by increasing not only thrust of an actuator but also speed when load pressure of the actuator increases. SOLUTION: A hydraulic circuit device of a construction machine is provided with a relief valve 11 to regulate maximum pressure of a delivery pipeline 40 of a hydraulic pump 2, a relief valve 13 which has relief set pressure higher than the relief valve 11 and regulates maximum pressure of a delivery pipeline 15 of a hydraulic pump 12, a merging pipeline 16 which is connected to the delivery pipeline 15 and merges pressure oil of the hydraulic pump 12 into a hydraulic cylinder 7, a solenoid directional control valve 14 which is arranged in the merging pipeline 16 and has a first position to cut off the merging pipeline 16 and a second position to communicate the merging pipeline 16 and a switch 31 to switch the solenoid directional control valve 14. Then, when the switch 31 is turned on, the solenoid directional control valve 14 is switched to the second position from the first position, and a fixed quantity of pressure oil is supplied to the bottom side of the hydraulic cylinder 7 by passing through the merging pipeline 16 from the hydraulic pump 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit device for a construction machine, and more particularly to a hydraulic circuit device for a construction machine capable of adjusting a maximum pressure of pressure oil supplied to an actuator to improve operability and workability of the actuator. The present invention relates to a hydraulic circuit device.

[0002]

2. Description of the Related Art There is a conventional hydraulic circuit device for construction machinery in which the maximum pressure of pressure oil supplied to an actuator can be adjusted. As an example, Japanese Patent Publication No. 7-116731 as shown in FIG. Some are listed.

In FIG. 16, a conventional hydraulic circuit device for a construction machine includes a prime mover 1, a variable displacement hydraulic pump 2 driven by the prime mover 1, and a discharge line 40 of the hydraulic pump 2.
The valve is controlled by a relief valve 3 for regulating the maximum pressure, a switch 8 for increasing the relief set pressure of the relief valve 3, a hydraulic cylinder 7 driven by hydraulic oil from the hydraulic pump 2, and an operating lever 6. A direction switching valve 5 for supplying and discharging the pressure oil of the pump 2 to and from the hydraulic cylinder 7 and a regulator 10 for controlling the discharge flow rate of the hydraulic pump 2 are provided.

Since the output torque of the prime mover 1 of the hydraulic pump 2 is limited, the regulator 10 controls the hydraulic pump 2 according to the discharge pressure of the hydraulic pump 2 so as to have a relationship as shown by a solid line in FIG. The maximum discharge flow rate (the maximum supply flow rate to the hydraulic cylinder 7) is controlled.

[0005] The relief valve 3 is set so that the relief set pressure increases when the switch 8 is turned on.
Here, if the relief set pressure of the relief valve 3 when the switch 8 is off is Pf, and the relief set pressure of the relief valve 3 when the switch 8 is on is Po (Pf <Po), the switch 8 is turned off. When the discharge pressure of the hydraulic pump 2 reaches Pf, as shown in a region A of FIG.
The relief valve 3 operates, and the supply flow rate of the pressure oil from the hydraulic pump 2 to the hydraulic cylinder 7 is lost, so that the movement of the hydraulic cylinder 7 stops. However, when the switch 8 is turned on, the relief set pressure of the relief valve 3 increases from Pf to Po, and as shown in a shaded area B in FIG.
Even if the discharge pressure of the hydraulic pump 2 reaches Pf, the hydraulic oil is supplied from the hydraulic pump 2 to the hydraulic cylinder 7 until it reaches Po, and the hydraulic cylinder 7 moves. That is, when the switch 8 is turned on, the thrust of the hydraulic cylinder 7 increases.

Here, the reason why the magnitude of the relief set pressure of the relief valve 3 is switched by operating the switch 8 without increasing the relief set pressure of the relief 3 from the beginning is that hydraulic equipment is normally used at a low pressure. Then, the durability of the hydraulic device is improved by using the hydraulic device at a high pressure only when necessary.

[0007]

However, the above-mentioned prior art has the following problems.

As shown in FIG. 17, assuming that the required flow rate of the hydraulic cylinder 7 is Q1, when the discharge pressure of the hydraulic pump 2 is equal to or less than P3, the required flow rate Q1 does not matter regardless of the magnitude of the discharge pressure of the hydraulic pump 2. Is supplied from the hydraulic pump 2 to the hydraulic cylinder 7. However, when the load pressure of the hydraulic cylinder 7 increases and the discharge pressure of the hydraulic pump 2 becomes higher than P3, as the discharge pressure of the hydraulic pump 2 increases,
The supply flow rate of the pressure oil from the hydraulic pump 2 to the hydraulic cylinder 7 decreases, and the speed of the hydraulic cylinder 7 decreases. In particular, after the discharge pressure of the hydraulic pump 2 reaches the vicinity of the relief set pressure Pf, the supply flow rate of the hydraulic oil from the hydraulic pump 2 to the hydraulic cylinder 7 is considerably reduced, and the speed of the hydraulic cylinder 7 that is satisfied by the operator is obtained. Can not be.

For this reason, if the load pressure of the hydraulic cylinder 7 increases and the operator turns on the switch 8, the thrust of the hydraulic cylinder 7 increases, but the speed of the hydraulic cylinder 7 that the operator satisfies cannot be obtained. Operability and workability cannot be obtained.

An object of the present invention is to provide a hydraulic circuit device for a construction machine capable of obtaining good operability and workability by increasing not only the thrust but also the speed of the actuator when the load pressure of the actuator is increased. It is to provide.

[0011]

(1) In order to achieve the above object, the present invention supplies a first hydraulic pump, an actuator, and pressure oil of the first hydraulic pump to the actuator. A directional valve,
In a hydraulic circuit device for a construction machine having a first relief valve for regulating a maximum pressure of a discharge line of the first hydraulic pump, a second hydraulic pump and a relief set higher than the first relief valve. A second relief valve that has a pressure and regulates a maximum pressure of a discharge line of a second hydraulic pump, a merge line that merges pressure oil of the second hydraulic pump with the actuator, and the merge line And a command signal generating means for generating a command signal for switching the merge switching valve.

In the present invention configured as described above,
Even if the load pressure of the actuator is increased by the command signal generation means and the discharge line of the first hydraulic pump reaches the maximum pressure regulated by the first relief valve, the discharge line of the second hydraulic pump Until the pressure reaches the maximum pressure regulated by the second relief valve, a command signal is generated to cause the hydraulic oil of the second hydraulic pump to merge with the actuator through the merging line, and the merging switching valve is switched. Therefore, when the load pressure of the actuator increases, not only the thrust but also the speed of the hydraulic cylinder 7 increases, and good operability and workability can be obtained.

(2) In the above (1), preferably,
The command signal generating means is a switch operated by an operator.

[0014] Thus, the joining of the pressure oil of the second hydraulic pump to the actuator can be selectively performed at the discretion of the operator.

(3) In the above (1), preferably, the command signal generating means detects a discharge pressure of the first hydraulic pump, and the command signal is generated based on a signal from the detecting means. Signal conversion means for generating a signal.

Accordingly, when the load pressure of the actuator becomes high and it is necessary to join the hydraulic oil from the second hydraulic pump, the hydraulic oil is automatically supplied from the second hydraulic pump to the actuator. And better operability and workability can be obtained.

(4) Further, in the above (1), preferably, the command signal generating means detects a load pressure of the actuator, and generates the command signal based on a signal from the detecting means. Signal conversion means.

Thus, similarly to the above (3), when the load pressure on the actuator becomes high, the second
Pressure oil can be supplied from the hydraulic pump to the actuator, and better operability and workability can be obtained.

(5) In the above (3) or (4), preferably, the merging switching valve is a proportional valve that changes an opening area in accordance with the command signal, and the signal converting means includes the detecting means. When the detected pressure reaches a predetermined pressure lower than the relief set pressure of the first relief valve, the switching of the junction switching valve is started, and as the detected pressure increases, the opening area of the junction switching valve is reduced. The command signal is generated to increase the value.

Accordingly, when the pressure detected by the detecting means reaches a predetermined pressure lower than the relief set pressure of the first relief valve, the acceleration of the actuator can be automatically started, and the start of the acceleration is started. In this case, the speed of the actuator can be smoothly increased without suddenly increasing the speed.

(6) In the above (5), preferably,
The relationship between the command signal and the opening area of the merge switching valve is determined by the pressure supplied to the actuator before and after the discharge pressure of the first hydraulic pump reaches the relief set pressure of the first relief valve. The oil flow rate is set so as to change continuously.

Accordingly, even when the discharge pressure of the first hydraulic pump reaches the relief set pressure of the first relief valve, the speed of the actuator does not suddenly decrease, and better operability and workability can be obtained. Can be

(7) In the above (3) or (4), preferably, the command signal generating means further includes a mode switch, and the merging switching is performed by the command signal only when the mode switch is switched. Switch the valve.

As a result, according to the judgment of the operator, even if the load pressure of the actuator is increased, the operation can be performed with low fuel consumption without the pressure oil being joined from the second hydraulic pump to the actuator, or the load pressure of the actuator can be increased. At times, the speed can be increased by automatically joining the pressure oil from the second hydraulic pump to the actuator.

(8) In the above (1), preferably,
The merging switching valve is configured to shut off the merging line, communicate a first position for flowing the pressure oil of a second hydraulic pump to a tank, and the merging line, and supply the pressure oil of the second hydraulic pump to the tank. A second position to be supplied to the actuator, and switching from the first position to the second position by the command signal.

Thus, in a normal state where the hydraulic oil is not joined from the second hydraulic pump to the actuator, the operating torque of the second hydraulic pump can be reduced to almost zero, and the energy loss by the second hydraulic pump can be reduced.

(9) In the above (1), preferably, the merge pipe is connected to an actuator line between the direction switching valve and the actuator.

Thus, the pressure oil of the second hydraulic pump can be joined to the actuator.

(10) Further, in the above (1), preferably, the merging pipe is connected to the feeder line on a downstream side of a load check valve provided in a feeder line of the directional control valve.

Thus, the pressure oil of the second hydraulic pump can be combined with the actuator, and the driving force of the actuator in two directions can be increased not only the thrust but also the speed of the actuator as described in (1) above. Also,
When the direction switching valve is not operated and the actuator is not driven, the switching valve for merging is switched due to a malfunction and the hydraulic oil of the second hydraulic pump is not supplied to the actuator even if the merging line is connected. The actuator is not driven even though the valve is not operated, and safety can be improved.

(11) In the above (1), preferably, the apparatus further comprises switching speed reducing means for lowering the switching speed at the time of switching the merging switching valve by the command signal.

As a result, the supply flow rate of the pressure oil from the second hydraulic pump to the actuator gradually increases with time until a predetermined time elapses after the switching of the junction switching valve. Since the entire amount of pressure oil from the second hydraulic pump is not suddenly supplied to the actuator immediately after the switching of the valve, fluctuations in the speed of the actuator can be reduced and shock can be prevented.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.

Referring to FIG. 1, a hydraulic circuit device for a construction machine according to the present invention includes a prime mover 1, a variable displacement hydraulic pump 2 driven by the prime mover 1, a regulator 10 for controlling the discharge flow rate of the hydraulic pump 2, A direction switching valve 5 that is switched by a hydraulic cylinder 7 and an operation lever 6 to supply and discharge pressure oil from the hydraulic pump 2 to the hydraulic cylinder 7, a hydraulic pump 12 driven by the prime mover 1, and a discharge of the hydraulic pump 2 A relief valve 11 for regulating the maximum pressure of the line 40;
A relief valve 13 having a higher relief set pressure than the relief valve 11 and regulating the maximum pressure of the discharge line 15 of the hydraulic pump 12, and a hydraulic pump 12 connected to the discharge line 15.
A joining line 16 for joining the hydraulic oil to the hydraulic cylinder 7;
An electromagnetic switching valve 14 provided in the merging line 16 and a switch 31 for switching the electromagnetic switching valve 14 are provided.

Since the output torque of the prime mover 1 of the hydraulic pump 2 is limited, the regulator 10 controls the hydraulic pump 2 according to the discharge pressure of the hydraulic pump 2 so that the relationship shown by the solid line in FIG. The maximum discharge flow rate (the maximum supply flow rate of the pressure oil to the hydraulic cylinder 7) is controlled.

The pressure oil from the hydraulic pump 2 is supplied to the discharge pipe 40
From the hydraulic pump 2 guided to the feeder line 41 when the direction switching valve 5 is switched to the position shown in FIG. Is supplied to the bottom side of the hydraulic cylinder 7 through the actuator line 43. When the directional control valve 5 is switched to the position shown in FIG.
Is supplied to the rod side of the hydraulic cylinder 7 through the actuator line 44. Further, when the direction switching valve 5 is at the position shown in FIG. 3C, the pressure oil from the hydraulic pump 2 flows to the tank 9 and is not supplied to the hydraulic cylinder 7.

The hydraulic pump 12 is a fixed displacement type hydraulic pump whose discharge pressure is high. The discharge flow rate of the hydraulic pump 12 is just before the discharge pressure of the hydraulic pump 2 reaches the relief set pressure P1 of the relief valve 11. More than the discharge flow rate.

The merging line 16 is connected to an actuator line 43 between the direction switching valve 5 and the hydraulic cylinder 7, whereby the hydraulic oil of the hydraulic pump 12 merges with the bottom side of the hydraulic cylinder 7.

The solenoid-operated switching valve 14 communicates the first position for shutting off the joining line 16 and allowing the pressure oil of the hydraulic pump 12 to flow into the tank 9 and the joining line 16, so that the hydraulic oil from the hydraulic pump 12 A second position for supplying to the cylinder 7,
When the switch 31 is off, no current is supplied from the power supply 30 and the switch 31 is in the first position shown. When the switch 31 is turned on, current is supplied from the power supply 30 and the switch is switched to the second position. Here, the switch 31 is turned on and off by an operator's operation.

The electromagnetic switching valve 14 has a switch 31
Is provided, a mechanical shockless mechanism 14a is provided to reduce the switching speed so as not to suddenly switch from the first position to the second position when turning on.

Next, the operation of the present embodiment configured as described above will be described.

When the operation lever 6 is operated to switch the direction switching valve 5 to the position shown in FIG. 7A, the hydraulic oil from the hydraulic pump 2 is supplied to the bottom side of the hydraulic cylinder 7. Assuming that the required flow rate of the hydraulic cylinder 7 at this time is Q1, when the discharge pressure of the hydraulic pump 2 becomes equal to or higher than P3 from the characteristics of the hydraulic pump 2 shown by the solid line in FIG. Supply to the hydraulic cylinder 7 becomes impossible, and the speed of the hydraulic cylinder 7 decreases. Further, when the discharge pressure of the hydraulic pump 2 reaches the relief set pressure P1 of the relief valve 11, the pressure oil from the hydraulic pump 2 is returned to the tank 9 by the relief valve 11, and is no longer supplied to the hydraulic cylinder 7, so that the hydraulic cylinder 7 Stops. However, when the operator turns on the switch 31 when the discharge pressure of the hydraulic pump 2 reaches the relief set pressure P1 of the relief valve 11, the electromagnetic switching valve 14 switches from the first position to the second position, and FIG. As shown by the shaded area in FIG.
2 is the relief set pressure P2 of the relief valve 13.
Until the hydraulic pump 12 reaches a certain amount, the constant amount of pressure oil is supplied from the hydraulic pump 12 to the bottom side of the hydraulic cylinder 7 through the merging line 16, so that the thrust of the hydraulic cylinder 7 increases and the speed of the hydraulic cylinder 7 is switched. It is faster than before turning on 31.

Therefore, according to this embodiment, when the load pressure of the hydraulic cylinder 7 increases, not only the thrust but also the speed of the hydraulic cylinder 7 can be increased, and good operability and workability can be obtained. Can be.

When the switch 31 is off, the electromagnetic switching valve 14 is at the first position in which the junction line 16 is shut off and the hydraulic oil of the hydraulic pump 12 flows to the tank 9. In normal times when the hydraulic pump 12 is not supplied to the cylinder 7, the operating torque of the hydraulic pump 12 can be reduced to almost zero, and the energy loss by the hydraulic pump 12 can be reduced.

Further, the electromagnetic switching valve 14 is provided with a mechanical shockless mechanism 14a for reducing the switching speed, and the hydraulic pump 12 is operated until a predetermined time elapses after the switch 31 is turned on. Since the supply flow rate to the hydraulic cylinder 7 gradually increases with time and the entire amount of the hydraulic oil of the hydraulic pump 12 does not join the hydraulic cylinder 7 immediately after the switch 31 is turned on, the switch 31 is turned on. The fluctuation of the speed of the hydraulic cylinder 7 immediately after the operation can be reduced, and the shock when the switch 31 is turned on can be prevented.

When the operator operates the switch 31, the hydraulic oil of the hydraulic pump 12 is supplied to the hydraulic cylinder 7.
Since it is determined whether or not to join the hydraulic oil, the joining of the hydraulic oil of the hydraulic pump 12 can be selectively performed at the discretion of the operator.

In this embodiment, the electromagnetic switching valve 14 is provided with a mechanical shockless mechanism 14a. However, an electromagnetic switching valve without the shockless mechanism 14a may be provided, or a mechanical shockless mechanism may be provided. Instead of 14a, FIG.
An electric shockless mechanism having a device for determining the current supplied to the electromagnetic switching valve 14 according to the time since the switch 31 is turned on using the relationship shown in FIG.

In the present embodiment, the merging line 16 is connected to the actuator line 43, and the hydraulic oil from the hydraulic pump 12 merges with the bottom side of the hydraulic cylinder 7. However, the merging line 16 is connected to the actuator line 43. 44, and the hydraulic oil from the hydraulic pump 12 may be joined to the rod side of the hydraulic cylinder 7. In this case, the same effect as described above can be obtained.

Further, in this embodiment, the actuator is the hydraulic cylinder 7, but may be a hydraulic motor.

A second embodiment of the present invention will be described with reference to FIG. In the drawing, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 4, the hydraulic circuit device of the present embodiment does not connect the merging line 16 in the hydraulic circuit device of the first embodiment shown in FIG.
It is connected to a feeder line 41 on the downstream side of the load check valve 4, and the other configuration is the same as that of the first embodiment.

In the present embodiment thus constructed, similarly to the first embodiment, the operation lever 6 is operated to switch the direction switching valve 5 to the position shown in FIG. Is supplied to the bottom side of the hydraulic cylinder 7, when the load pressure of the hydraulic cylinder 7 increases and the switch 31 is turned on, the pressure oil from the hydraulic pump 12 is supplied to the bottom side of the hydraulic cylinder 7. Similarly to the first embodiment, when the load pressure of the hydraulic cylinder 7 increases, not only the thrust of the hydraulic cylinder 7 but also the speed can be increased.

In this embodiment, the merging line 1
6 is a feeder line 41 downstream of the load check valve 4
, The operation lever 6 is operated to switch the direction switching valve 5 to the position shown in FIG.
When the switch 31 is turned on, the hydraulic oil from the hydraulic pump 12 is supplied to the rod side of the hydraulic cylinder 7 in the same manner as in the first embodiment even when the hydraulic oil from the hydraulic cylinder 7 is supplied to the rod side of the hydraulic cylinder 7. Also in this case, similarly to the first embodiment, when the load pressure of the hydraulic cylinder 7 increases, not only the thrust but also the speed of the hydraulic cylinder 7 can be increased.

Further, the merging line 16 is connected to the load check valve 4.
Is connected to the feeder line 41 on the downstream side of
When the operation lever 6 is not operated and the direction switching valve 5 is at the position shown in FIG. C and the hydraulic cylinder 7 is not driven, the hydraulic oil of the hydraulic pump 12 is not supplied to the hydraulic cylinder 7 even if the switch 31 is turned on. Therefore, even though the operation lever 6 is not operated, the hydraulic cylinder 7 is not driven due to a malfunction of the switch 31, and safety can be improved.

As described above, according to the present embodiment, when the load pressure of the hydraulic cylinder 7 is increased in the two directions of the extension direction and the contraction direction of the hydraulic cylinder 7, if only the thrust of the hydraulic cylinder 7 is satisfied, The speed can be increased, and when the directional control valve 5 is not operated, the pressure oil of the hydraulic pump 12 is not supplied to the hydraulic cylinder 7, so that the safety can be improved.

In the present embodiment, the merging line 16 is connected to the feeder line 41 downstream of the load check valve 4, but may be connected to the discharge line 40 of the hydraulic pump 2.

A third embodiment of the present invention will be described with reference to FIGS. In the drawing, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 5, the hydraulic circuit device of the present embodiment is provided in a merging line instead of the electromagnetic switching valve 14, the power supply 30 and the switch 31 in the hydraulic circuit device of the first embodiment shown in FIG. An electromagnetic proportional switching valve 20 that changes the opening area according to a command signal, a pump discharge pressure sensor 21 that detects the discharge pressure of the hydraulic pump 2, and a command to the electromagnetic proportional switching valve 20 based on a signal from the pump discharge pressure sensor 21. It has a controller 22 as signal conversion means for generating a signal (output current I) and a mode switch 23 operated by an operator, and the other configuration is the same as that of the first embodiment.

The electromagnetic proportional switching valve 20 communicates with the first position for shutting off the joining line 16 and allowing the hydraulic oil of the hydraulic pump 12 to flow into the tank 9 and the joining line 16 to allow the hydraulic oil from the hydraulic pump 12 to flow therethrough. And a second position for supplying to the hydraulic cylinder 7.
When the output current I is supplied from the controller 22, the switching from the first position to the second position is started. As shown in FIG. 6, as the output current I increases, the opening area of the first position decreases while the second position decreases. When the opening area of the position increases and the output current I reaches a predetermined value I1, the position is completely switched to the second position.

As shown in FIG. 7, the controller 22
The output current I is obtained from the detection signal from the pump discharge pressure sensor 21 using the relationship shown in the drawing, and is output to the solenoid 20a of the electromagnetic proportional switching valve 20. According to FIG. 7, the output current I output to the solenoid 20a of the electromagnetic proportional switching valve 20 is shown.
Is the hydraulic pump 2 detected by the pump discharge pressure sensor 21.
Discharge pressure P is the relief set pressure P1 of the relief valve 11.
It is generated when the pressure reaches a lower predetermined pressure P0, increases as the discharge pressure P of the hydraulic pump 2 increases, and reaches a maximum value I1 when the discharge pressure P of the hydraulic pump 2 reaches the relief set pressure P1. As a result, when the discharge pressure P of the hydraulic pump 2 detected by the pump discharge pressure sensor 21 reaches a predetermined pressure P0 lower than the relief set pressure P1 of the relief valve 11, as shown in FIG. The output current I is supplied to the switching valve 20, the electromagnetic proportional switching valve 20 starts switching from the first position to the second position, and the opening area of the first position decreases as the discharge pressure P of the hydraulic pump 2 increases. When the opening area of the second position increases and the discharge pressure P of the hydraulic pump 2 reaches the relief set pressure P1, the maximum value I1 of the output current I is given to the electromagnetic proportional switching valve 20, and the electromagnetic proportional switching valve 20 Is completely switched to the first position.

The mode switch 23 has two modes, on and off. When the mode switch 23 is on, the output current I generated by the controller 22 is guided to the electromagnetic proportional switching valve 20. When the mode switch 23 is off, the output current I Even if the current I is generated, it is not guided to the electromagnetic proportional switching valve 20.

In this embodiment, the mode switch 23 is turned on, and when the load pressure of the hydraulic cylinder 7 increases and the discharge pressure P of the hydraulic pump 2 reaches a predetermined pressure P0, the electromagnetic switch is turned off. Proportional switching valve 20 is the first
The position is switched from the position to the second position, and the pressure oil from the hydraulic pump 12 starts to join the hydraulic cylinder 7, and as the discharge pressure P of the hydraulic pump 2 becomes higher than P0, the opening area of the second position becomes larger and the hydraulic pump 12 The flow rate of the pressure oil supplied to the hydraulic cylinder 7 from is increased. And the hydraulic pump 2
Discharge pressure P is the relief set pressure P1 of the relief valve 11.
Is reached, the hydraulic oil supplied from the hydraulic pump 2 to the hydraulic cylinder 7 is exhausted, but the electromagnetic proportional switching valve 20 is completely switched to the second position, and the opening area of the second position is maximized, Until the discharge pressure of 12 reaches the relief set pressure P2 of the relief valve 13, the hydraulic pump 12 supplies the maximum flow of hydraulic oil to the hydraulic cylinder 7.

Therefore, as shown in FIG. 9, when the required flow rate of the hydraulic cylinder 7 is assumed to be Q1, if the discharge pressure P of the hydraulic pump 2 becomes P3 or more, the required flow rate Q1
Can no longer be supplied to the hydraulic cylinder 7 and the speed of the hydraulic cylinder 7 decreases, but the discharge pressure P
Reaches a predetermined pressure P0, the pressure oil of the hydraulic pump 12 starts to join the hydraulic cylinder 7, so that the speed of the hydraulic cylinder 7 decreases to a small extent, and the discharge pressure P of the hydraulic pump 2 decreases , The hydraulic oil of the hydraulic pump 2 is no longer supplied to the hydraulic cylinder 7, but the maximum flow rate of the hydraulic oil of the hydraulic pump 12 is supplied to the hydraulic cylinder 7. Therefore, the speed of the hydraulic cylinder 7 when the discharge pressure P of the hydraulic pump 2 reaches the vicinity of the relief set pressure P1 is increased, and the load pressure of the hydraulic cylinder 7 is higher than in the case of the single supply by the conventional hydraulic pump 2. Therefore, even when a pump discharge pressure higher than the relief set pressure P1 is required, the hydraulic cylinder 7 is driven at a speed higher than the speed near the relief set pressure P1 in the case of the single supply by the conventional hydraulic pump 2. Therefore, in the present embodiment, as in the first embodiment, when the load pressure of the hydraulic cylinder 7 increases, the hydraulic cylinder 7
Not only the thrust but also the speed can be increased, and when the mode switch 23 is turned on, the load pressure of the actuator increases, and when the hydraulic oil from the second hydraulic pump needs to be joined, The pressure oil can be automatically supplied from the second hydraulic pump to the actuator, so that better operability and workability can be obtained.

Further, the electromagnetic proportional switching valve 20 determines that the discharge pressure P of the hydraulic pump 2 is lower than the relief set pressure P of the relief valve 11.
When a predetermined pressure P0 lower than 1 is reached, switching from the first position to the second position is started, and the controller 22 controls the opening area of the second position to increase as the discharge pressure P of the hydraulic pump 2 increases. Hydraulic pump 2
When the discharge pressure P reaches a predetermined pressure P0, the speed of the hydraulic cylinder 7 can be automatically started to increase, and at the start of the speed increase, the speed of the hydraulic cylinder 7 does not suddenly increase but increases smoothly. Can be faster.

Further, when the mode switch 23 is turned off, or even when the mode switch 23 is turned on, the discharge pressure P of the hydraulic pump 2 is set to a predetermined pressure P0.
Before reaching the first position, the first position is established because the merging line 16 is shut off and the pressure oil of the hydraulic pump 12 flows into the tank 9.
As in the embodiment, the energy loss due to the hydraulic pump 12 can be reduced during normal times when the hydraulic oil of the hydraulic pump 12 is not supplied to the hydraulic cylinder 7.

Since the mode switch 23 is provided,
According to the judgment of the operator, even if the load pressure of the hydraulic cylinder 7 is increased, the operation is performed with low fuel consumption without converging the hydraulic oil from the hydraulic pump 12 to the hydraulic cylinder 7 or when the load pressure of the hydraulic cylinder 7 is increased. The pressure oil can be automatically joined from the hydraulic pump 12 to the hydraulic cylinder 7 to increase the speed of the hydraulic cylinder 7.

FIGS. 10 to 12 show a fourth embodiment of the present invention.
This will be described with reference to FIG. In the drawing, the same members as those shown in FIGS. 1 and 5 are denoted by the same reference numerals, and description thereof will be omitted.

The hydraulic circuit device according to the present embodiment has a third
This embodiment has a controller 22A in which the processing function of the controller 22 in the third embodiment is changed, and the other configuration is the same as that of the third embodiment shown in FIG.

The controller 22A differs from the controller 22 of the third embodiment shown in FIG. 7 in the relationship between the discharge pressure P of the hydraulic pump 2 and the output current I, as shown in FIG. . That is, as compared with the third embodiment, the increase amount of the output current I after the discharge pressure P of the hydraulic pump 2 reaches the predetermined pressure P0 is small, and the discharge pressure P of the hydraulic pump 2 is close to the relief set pressure P1. , The output current I sharply increases.

As a result, the relationship between the discharge pressure P of the hydraulic pump 2 as shown in FIG. 11 and the opening area A of the electromagnetic proportional switching valve 20 is obtained, and as shown by the dashed line in FIG. Before and after the pressure reaches the relief set pressure P1 of the relief valve 11, the maximum flow rate of the pressure oil supplied to the hydraulic cylinder 7 changes continuously.

For this reason, as in the third embodiment, when the discharge pressure P of the hydraulic pump 2 reaches a predetermined pressure P0, the hydraulic oil of the hydraulic pump 12 starts to join the hydraulic cylinder 7, and the hydraulic pump 2 When the discharge pressure P reaches the relief set pressure P1, the maximum flow rate of the pressure oil of the hydraulic pump 12 becomes
And the speed of the hydraulic cylinder 7 does not suddenly decrease even when the discharge pressure P of the hydraulic pump 2 reaches the relief set pressure P1.

As described above, also in the present embodiment, the third
And the controller 22A continuously changes the flow rate of the pressure oil supplied to the hydraulic cylinder 7 before and after the discharge pressure P of the hydraulic pump 2 reaches the relief set pressure P1. The opening area of the electromagnetic proportional switching valve 20 is controlled so that the speed of the hydraulic cylinder 7 does not suddenly decrease even when the discharge pressure P of the hydraulic pump 2 reaches the relief set pressure P1, so that a more favorable Operability and workability are obtained.

FIGS. 13 to 15 show a fifth embodiment of the present invention.
This will be described with reference to FIG. In the drawing, the same members as those shown in FIGS. 1 and 5 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 13, a hydraulic circuit device according to the present embodiment comprises a cylinder load pressure sensor 25 for detecting the load pressure of the hydraulic cylinder 7 instead of the pump discharge pressure sensor 21 and the controller 22 in the third embodiment.
It has a controller 22B having a different processing function, and the other configuration is the same as that of the third embodiment.

As shown in FIG. 14, the controller 22B obtains an output current I from the detection signal from the cylinder load pressure sensor 25 using the relationship shown in the drawing and outputs the output current I to the solenoid 20a of the electromagnetic proportional switching valve 20. . Here, the relationship shown in the figure corresponds to the controller 2 of the third embodiment shown in FIG.
The horizontal axis of the relationship in 2 is the load pressure PL of the hydraulic cylinder 7
It is what it was.

As a result, the load pressure PL of the hydraulic cylinder 7 is
The relationship between the pressure and the supply flow rate Q to the hydraulic cylinder 7 is as shown in FIG. 15, and the hydraulic oil of the hydraulic pump 12 is joined to the hydraulic cylinder 7 in the same manner as in the third embodiment.

Therefore, in the present embodiment, the same effects as in the third embodiment can be obtained.

[0078]

According to the present invention, when the load pressure of the actuator is increased, not only the thrust but also the speed of the actuator can be increased, and good operability and workability can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a hydraulic circuit device of a construction machine according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and a supply flow rate to a hydraulic cylinder.

FIG. 3 is a diagram illustrating a relationship between an elapsed time after a switch is turned on and a current supplied to an electromagnetic proportional valve.

FIG. 4 is a diagram illustrating a hydraulic circuit device of a construction machine according to a second embodiment of the present invention.

FIG. 5 is a diagram illustrating a hydraulic circuit device of a construction machine according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between an output current from a controller and an opening area of an electromagnetic proportional switching valve.

FIG. 7 is a diagram showing a processing function of a controller.

FIG. 8 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and an opening area of an electromagnetic proportional switching valve.

FIG. 9 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and a supply flow rate to a hydraulic cylinder.

FIG. 10 is a diagram illustrating processing functions of a controller according to a fourth embodiment of the present invention.

FIG. 11 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and an opening area of an electromagnetic proportional switching valve.

FIG. 12 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and a supply flow rate to a hydraulic cylinder.

FIG. 13 is a diagram illustrating a hydraulic circuit device of a construction machine according to a fifth embodiment of the present invention.

FIG. 14 is a diagram showing a processing function of a controller.

FIG. 15 is a diagram showing a relationship between a load pressure of a hydraulic cylinder and a flow rate supplied to the hydraulic cylinder.

FIG. 16 is a view showing a conventional hydraulic circuit device of a construction machine.

FIG. 17 is a diagram showing a relationship between a discharge pressure of a hydraulic pump and a supply flow rate to a hydraulic cylinder.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 prime mover 2 hydraulic pump 3 relief valve 4 load check valve 5 direction switching valve 6 operating lever 7 hydraulic cylinder 9 tank 10 regulator 11 relief valve 12 hydraulic pump 13 relief valve 14 electromagnetic switching valve 14a shockless mechanism 15 discharge pipe 16 merge pipe Path 20 Electromagnetic proportional switching valve 21 Pump discharge pressure sensor 22, 22A, 22B Controller 23 Mode switch 25 Cylinder load pressure sensor 30 Power supply 31 Switch 40 Discharge line 41 Feeder line 43, 44 Actuator line

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Tsukasa Toyooka 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. (72) Inventor Takeshi Nakamura 650, Kandamachi, Tsuchiura-shi, Ibaraki Hitachi Construction Machinery Co., Ltd. Tsuchiura factory

Claims (11)

[Claims] 1. A first hydraulic pump, an actuator,
A hydraulic circuit for a construction machine having a direction switching valve for supplying and discharging the pressure oil of the first hydraulic pump to and from the actuator, and a first relief valve for regulating a maximum pressure of a discharge line of the first hydraulic pump. A second relief pump having a higher relief set pressure than the first relief valve and regulating a maximum pressure of a discharge line of the second hydraulic pump; A junction line for joining the hydraulic oil of the second hydraulic pump to the actuator, a junction switching valve provided in the junction line, and a command signal generating means for generating a command signal for switching the junction switching valve. A hydraulic circuit device for a construction machine, comprising: 2. The hydraulic circuit device for a construction machine according to claim 1, wherein said command signal generating means is a switch operated by an operator. 3. The hydraulic circuit device for a construction machine according to claim 1, wherein said command signal generating means detects a discharge pressure of said first hydraulic pump, and said command signal generating means detects a discharge pressure of said first hydraulic pump based on a signal from said detecting means. A hydraulic circuit device for a construction machine, comprising: signal conversion means for generating a command signal. 4. The hydraulic circuit device for a construction machine according to claim 1, wherein said command signal generating means detects a load pressure of said actuator, and generates said command signal based on a signal from said detecting means. A hydraulic circuit device for a construction machine, comprising: 5. The hydraulic circuit device for a construction machine according to claim 3, wherein the junction switching valve is a proportional valve that changes an opening area in accordance with the command signal, and the signal conversion unit performs the detection. When the pressure detected by the means reaches a predetermined pressure lower than the relief set pressure of the first relief valve, the switching of the junction switching valve is started, and the opening area of the junction switching valve is increased as the detected pressure increases. The hydraulic circuit device for a construction machine, wherein the command signal is generated so as to increase the hydraulic pressure. 6. The hydraulic circuit device for a construction machine according to claim 5, wherein the relation between the command signal and the opening area of the merge switching valve is such that the discharge pressure of the first hydraulic pump is equal to the first pressure.
A hydraulic circuit device for a construction machine, wherein a flow rate of pressure oil supplied to the actuator is set to change continuously before and after reaching a relief set pressure of the relief valve. 7. The hydraulic circuit device for a construction machine according to claim 3, wherein said command signal generating means further includes a mode switch, and said merging unit is provided by said command signal only when said mode switch is switched. A hydraulic circuit device for a construction machine characterized by switching a switching valve. 8. The hydraulic circuit device for a construction machine according to claim 1, wherein the junction switching valve shuts off the junction line.
A first position for flowing pressure oil of a second hydraulic pump to a tank, and a second position for communicating pressure oil of a second hydraulic pump to the actuator, the second position being in communication with the merging line; The hydraulic circuit device for a construction machine is switched from the first position to the second position. 9. The hydraulic circuit device for a construction machine according to claim 1, wherein said merging line is connected to an actuator line between said directional switching valve and said actuator. Circuit device. 10. The hydraulic circuit device for a construction machine according to claim 1, wherein the merging line is connected to the feeder line on a downstream side of a load check valve provided on a feeder line of the direction switching valve. A hydraulic circuit device for a construction machine, comprising: 11. The construction machine hydraulic circuit device according to claim 1, further comprising a switching speed reducing means for reducing a switching speed at the time of switching of said merging switching valve by said command signal. Hydraulic circuit device.